弄岗喀斯特季节性雨林枯立木多度的空间分布及影响因子

Abstract

Standing dead trees are an important part of the composition of forest structure. Therefore, studying the spatial distribution of standing dead trees abundance and its impact factors has provided much needed insights to understand the mechanism of tree death and the succession of community. According to a 15-hm2 study plot investigation in northern tropical karst seasonal rain forest, Nonggang, southern China, the standing dead trees with DBH(diameter at breast height) greater than 1 cm were classified. And the spatial distribution of standing dead trees abundance and its impact factors like spatial, topographic and communities' were analyzed using zero-inflated negative binomial models. The results showed that:(1) there were 2254 standing dead trees in the plot with an average DBH of 6.21 cm. And the maximum DBH was 61.86 cm. The DBH size-class structure of standing dead trees exhibited an inverse J-shaped pattern. Dead trees with smaller DBH distributed more densely in the high elevation areas, whereas those with larger DBH had a higher density in the valley bottoms.(2) Standing dead trees with smaller DBH displayed an clumped distribution, while those with larger DBHs had a random distribution. And the abundance of standing dead trees displayed different spatial autocorrelation at different spatial scales.(3) As DBH size-class increased, the correlation between abundance and elevation, abundance and slope gradually increased, while that of abundance and convex, abundance and spatial adjacent factors gradually decreased. The correlation between abundance and spatial adjacent factors increased as unit spatial scale increased, and the correlation between abundance and convex, elevation, slope and community type factors gradually decreased as unit spatial scale increased. There were different spatial distribution of standing dead trees abundance existed as the scales changed. And the spatial, topographic factors, different communities have significant impact on these spatial patterns of standing dead trees abundance and the diameter class structure. In turn, the spatial distributions of standing dead trees have significant influence on the light resources and the distribution of woody debris, and then impact the species composition of communities.